In recent years, thermoplastic composite materials have been provided to form articles. For example, such a thermoplastic composite material is disclosed in U.S. Pat. No. 4,778,717, issued to Douglas Fitchmun on Oct. 18, 1988, for a "Thermoplastic Thermoformable Composite Material" and assigned of record to the assignee of record in this application. The thermoplastic composite material in U.S. Pat. No. 4,778,717 is formed from a thermoplastic core and from layers of a fabric impregnated and covered with a thermoplastic material. Such fabric-coated material is bonded to the core to form the thermoplastic composite material.
Subsequently a simplified thermoplastic material was developed by applicant's assignee. This simplified thermoplastic composite material also included a fabric impregnated and covered with a thermoplastic material. However, it eliminated the thermoplastic core and the second layer of fabric on the other side of the core. It may be formed from a single layer of the fabric impregnated and covered with the thermoplastic material or it may be formed from a plurality of such layers.
The materials discussed in the previous paragraphs have several advantages. They are light in weight but strong. They can be shaped in a desired three-dimensional representation by the application of heat to the thermoplastic composite material and the disposition of the heated material on a mold of the desired shape. If the shape is imperfect, the thermoplastic composite material can be heated and reshaped again.
The materials discussed in the previous paragraphs have certain disadvantages. One disadvantages is that the thickness of the material is not uniform at different positions on the article if such uniformity is desired when the material is formed into complex three-dimensional shapes. Another disadvantage is that the materials tend to wrinkle when they have to be shaped into a complex pattern. This is undesirable when the shaped piece has to have a smooth appearance without wrinkles. It is also not desirable from a structural standpoint. For example, the shaped piece should be free of wrinkles when it constitutes the shell of a helmet. The shaped piece should also be free of wrinkles when it constitutes the base portion (extending approximately to the ankles) of footwear which is worn by a skater, particularly when the footwear is for an ice skate or a skate with in-line rollers. The materials discussed above have also been disadvantageous because they have had to be shaped at elevated temperatures.
The problems discussed in this paragraph have been in existence for some time. Attempts have been made to resolve such problems but without much success. Products formed from thermoplastic composite materials with complex shapes have not had a uniform thicknesses when desired or have not been provided with specified thickness at different positions. Furthermore, the products have been wrinkled even when formed at elevated temperatures.
This invention provides a method of forming, at ambient temperatures, articles of complex shape without wrinkles even when the articles have complex shapes or are highly contoured. Furthermore, the articles can be formed with specified (non-uniform or uniform) thicknesses at different positions. This invention also relates to the thermoplastic composite materials before the curing, to the thermoplastic composite materials after the curing, and to articles formed from such thermoplastic composite materials by such methods.